Antiplatelets and anticoagulants (blood thinners) -- Passionflower may increase the amount of time blood needs to clot, so it could make the effects of blood-thinning medications stronger and increase your risk of bleeding. Blood-thinning drugs include:

Clopidogrel (Plavix)

Warfarin (Coumadin)

Monoamine oxidase inhibitors (MAO inhibitors or MAOIs) -- MAO inhibitors are an older class of antidepressants that are not often prescribed now. Theoretically, passionflower might increase the effects of MAO inhibitors, as well as their side effects, which can be dangerous. These drugs include: